A retractable knife of the above-mentioned type was described in detail in my prior U.S. Pat. No. 3,192,624 issued on July 6, 1965. In this utility knife, one of the important members is a blade carrier which is axially movable within the handle to extend or to retract the blade. This carrier is an oval loop of a tough resilient plastic provided with a forward extending rigid arm to support the blade in its central rectangular aperture and also with a flexible rear arm to bias a rear portion of the blade in one transversal direction. The carrier carriers a control button and normally locked detents which, when the button is depressed, are temporarily released to allow shifting of the carrier and the blade in a selected axial position. My prior patented utility knife, although satisfactory in most instances, cannot readily accomodate the variety of different types of utility blades commercially available.
Such commercially available utility blades generally fall into two categories, i.e. those having three notches on the edge opposite the cutting edge with a central blade aperture for stability of the blade during cutting such as illustrated in my prior U.S. Pat. Nos. 3,906,625 and 4,005,525, and, solid blades having only two notches on the edge opposite the cutting edge. In certain cutting applications, use of the solid blade type is preferred, whereas in other cutting applications use of the apertured blade type is preferred. However, applicant is not aware of any commerically available utility knives which readily accommodate both types of blades on a common blade carrier, where aperture indent springs out of way. For example, when it is attempted to use a solid type blade on the blade carrier of my prior U.S. Pat. No. 3,192,624, the blade cannot satisfactorily be mounted on the center and, thus, the utility knife cannot operate properly. Thus, my prior patented knife, although satisfactory for cutting applications in which an apertured blade is employed, cannot readily be used with a solid type blade as well. This disadvantage of the prior art are overcome by the present invention.